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<pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a>
<span class="sourceLineNo">002</span> * Copyright (C) 2007 The Guava Authors<a name="line.2"></a>
<span class="sourceLineNo">003</span> *<a name="line.3"></a>
<span class="sourceLineNo">004</span> * Licensed under the Apache License, Version 2.0 (the "License");<a name="line.4"></a>
<span class="sourceLineNo">005</span> * you may not use this file except in compliance with the License.<a name="line.5"></a>
<span class="sourceLineNo">006</span> * You may obtain a copy of the License at<a name="line.6"></a>
<span class="sourceLineNo">007</span> *<a name="line.7"></a>
<span class="sourceLineNo">008</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.8"></a>
<span class="sourceLineNo">009</span> *<a name="line.9"></a>
<span class="sourceLineNo">010</span> * Unless required by applicable law or agreed to in writing, software<a name="line.10"></a>
<span class="sourceLineNo">011</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.11"></a>
<span class="sourceLineNo">012</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.12"></a>
<span class="sourceLineNo">013</span> * See the License for the specific language governing permissions and<a name="line.13"></a>
<span class="sourceLineNo">014</span> * limitations under the License.<a name="line.14"></a>
<span class="sourceLineNo">015</span> */<a name="line.15"></a>
<span class="sourceLineNo">016</span><a name="line.16"></a>
<span class="sourceLineNo">017</span>package com.google.common.base;<a name="line.17"></a>
<span class="sourceLineNo">018</span><a name="line.18"></a>
<span class="sourceLineNo">019</span>import static com.google.common.base.Preconditions.checkNotNull;<a name="line.19"></a>
<span class="sourceLineNo">020</span><a name="line.20"></a>
<span class="sourceLineNo">021</span>import com.google.common.annotations.Beta;<a name="line.21"></a>
<span class="sourceLineNo">022</span><a name="line.22"></a>
<span class="sourceLineNo">023</span>import java.io.PrintWriter;<a name="line.23"></a>
<span class="sourceLineNo">024</span>import java.io.StringWriter;<a name="line.24"></a>
<span class="sourceLineNo">025</span>import java.util.ArrayList;<a name="line.25"></a>
<span class="sourceLineNo">026</span>import java.util.Collections;<a name="line.26"></a>
<span class="sourceLineNo">027</span>import java.util.List;<a name="line.27"></a>
<span class="sourceLineNo">028</span><a name="line.28"></a>
<span class="sourceLineNo">029</span>import javax.annotation.Nullable;<a name="line.29"></a>
<span class="sourceLineNo">030</span><a name="line.30"></a>
<span class="sourceLineNo">031</span>/**<a name="line.31"></a>
<span class="sourceLineNo">032</span> * Static utility methods pertaining to instances of {@link Throwable}.<a name="line.32"></a>
<span class="sourceLineNo">033</span> *<a name="line.33"></a>
<span class="sourceLineNo">034</span> * &lt;p&gt;See the Guava User Guide entry on &lt;a href=<a name="line.34"></a>
<span class="sourceLineNo">035</span> * "http://code.google.com/p/guava-libraries/wiki/ThrowablesExplained"&gt;<a name="line.35"></a>
<span class="sourceLineNo">036</span> * Throwables&lt;/a&gt;.<a name="line.36"></a>
<span class="sourceLineNo">037</span> *<a name="line.37"></a>
<span class="sourceLineNo">038</span> * @author Kevin Bourrillion<a name="line.38"></a>
<span class="sourceLineNo">039</span> * @author Ben Yu<a name="line.39"></a>
<span class="sourceLineNo">040</span> * @since 1.0<a name="line.40"></a>
<span class="sourceLineNo">041</span> */<a name="line.41"></a>
<span class="sourceLineNo">042</span>public final class Throwables {<a name="line.42"></a>
<span class="sourceLineNo">043</span>  private Throwables() {}<a name="line.43"></a>
<span class="sourceLineNo">044</span><a name="line.44"></a>
<span class="sourceLineNo">045</span>  /**<a name="line.45"></a>
<span class="sourceLineNo">046</span>   * Propagates {@code throwable} exactly as-is, if and only if it is an<a name="line.46"></a>
<span class="sourceLineNo">047</span>   * instance of {@code declaredType}.  Example usage:<a name="line.47"></a>
<span class="sourceLineNo">048</span>   * &lt;pre&gt;<a name="line.48"></a>
<span class="sourceLineNo">049</span>   *   try {<a name="line.49"></a>
<span class="sourceLineNo">050</span>   *     someMethodThatCouldThrowAnything();<a name="line.50"></a>
<span class="sourceLineNo">051</span>   *   } catch (IKnowWhatToDoWithThisException e) {<a name="line.51"></a>
<span class="sourceLineNo">052</span>   *     handle(e);<a name="line.52"></a>
<span class="sourceLineNo">053</span>   *   } catch (Throwable t) {<a name="line.53"></a>
<span class="sourceLineNo">054</span>   *     Throwables.propagateIfInstanceOf(t, IOException.class);<a name="line.54"></a>
<span class="sourceLineNo">055</span>   *     Throwables.propagateIfInstanceOf(t, SQLException.class);<a name="line.55"></a>
<span class="sourceLineNo">056</span>   *     throw Throwables.propagate(t);<a name="line.56"></a>
<span class="sourceLineNo">057</span>   *   }<a name="line.57"></a>
<span class="sourceLineNo">058</span>   * &lt;/pre&gt;<a name="line.58"></a>
<span class="sourceLineNo">059</span>   */<a name="line.59"></a>
<span class="sourceLineNo">060</span>  public static &lt;X extends Throwable&gt; void propagateIfInstanceOf(<a name="line.60"></a>
<span class="sourceLineNo">061</span>      @Nullable Throwable throwable, Class&lt;X&gt; declaredType) throws X {<a name="line.61"></a>
<span class="sourceLineNo">062</span>    // Check for null is needed to avoid frequent JNI calls to isInstance().<a name="line.62"></a>
<span class="sourceLineNo">063</span>    if (throwable != null &amp;&amp; declaredType.isInstance(throwable)) {<a name="line.63"></a>
<span class="sourceLineNo">064</span>      throw declaredType.cast(throwable);<a name="line.64"></a>
<span class="sourceLineNo">065</span>    }<a name="line.65"></a>
<span class="sourceLineNo">066</span>  }<a name="line.66"></a>
<span class="sourceLineNo">067</span><a name="line.67"></a>
<span class="sourceLineNo">068</span>  /**<a name="line.68"></a>
<span class="sourceLineNo">069</span>   * Propagates {@code throwable} exactly as-is, if and only if it is an<a name="line.69"></a>
<span class="sourceLineNo">070</span>   * instance of {@link RuntimeException} or {@link Error}.  Example usage:<a name="line.70"></a>
<span class="sourceLineNo">071</span>   * &lt;pre&gt;<a name="line.71"></a>
<span class="sourceLineNo">072</span>   *   try {<a name="line.72"></a>
<span class="sourceLineNo">073</span>   *     someMethodThatCouldThrowAnything();<a name="line.73"></a>
<span class="sourceLineNo">074</span>   *   } catch (IKnowWhatToDoWithThisException e) {<a name="line.74"></a>
<span class="sourceLineNo">075</span>   *     handle(e);<a name="line.75"></a>
<span class="sourceLineNo">076</span>   *   } catch (Throwable t) {<a name="line.76"></a>
<span class="sourceLineNo">077</span>   *     Throwables.propagateIfPossible(t);<a name="line.77"></a>
<span class="sourceLineNo">078</span>   *     throw new RuntimeException("unexpected", t);<a name="line.78"></a>
<span class="sourceLineNo">079</span>   *   }<a name="line.79"></a>
<span class="sourceLineNo">080</span>   * &lt;/pre&gt;<a name="line.80"></a>
<span class="sourceLineNo">081</span>   */<a name="line.81"></a>
<span class="sourceLineNo">082</span>  public static void propagateIfPossible(@Nullable Throwable throwable) {<a name="line.82"></a>
<span class="sourceLineNo">083</span>    propagateIfInstanceOf(throwable, Error.class);<a name="line.83"></a>
<span class="sourceLineNo">084</span>    propagateIfInstanceOf(throwable, RuntimeException.class);<a name="line.84"></a>
<span class="sourceLineNo">085</span>  }<a name="line.85"></a>
<span class="sourceLineNo">086</span><a name="line.86"></a>
<span class="sourceLineNo">087</span>  /**<a name="line.87"></a>
<span class="sourceLineNo">088</span>   * Propagates {@code throwable} exactly as-is, if and only if it is an<a name="line.88"></a>
<span class="sourceLineNo">089</span>   * instance of {@link RuntimeException}, {@link Error}, or<a name="line.89"></a>
<span class="sourceLineNo">090</span>   * {@code declaredType}. Example usage:<a name="line.90"></a>
<span class="sourceLineNo">091</span>   * &lt;pre&gt;<a name="line.91"></a>
<span class="sourceLineNo">092</span>   *   try {<a name="line.92"></a>
<span class="sourceLineNo">093</span>   *     someMethodThatCouldThrowAnything();<a name="line.93"></a>
<span class="sourceLineNo">094</span>   *   } catch (IKnowWhatToDoWithThisException e) {<a name="line.94"></a>
<span class="sourceLineNo">095</span>   *     handle(e);<a name="line.95"></a>
<span class="sourceLineNo">096</span>   *   } catch (Throwable t) {<a name="line.96"></a>
<span class="sourceLineNo">097</span>   *     Throwables.propagateIfPossible(t, OtherException.class);<a name="line.97"></a>
<span class="sourceLineNo">098</span>   *     throw new RuntimeException("unexpected", t);<a name="line.98"></a>
<span class="sourceLineNo">099</span>   *   }<a name="line.99"></a>
<span class="sourceLineNo">100</span>   * &lt;/pre&gt;<a name="line.100"></a>
<span class="sourceLineNo">101</span>   *<a name="line.101"></a>
<span class="sourceLineNo">102</span>   * @param throwable the Throwable to possibly propagate<a name="line.102"></a>
<span class="sourceLineNo">103</span>   * @param declaredType the single checked exception type declared by the<a name="line.103"></a>
<span class="sourceLineNo">104</span>   *     calling method<a name="line.104"></a>
<span class="sourceLineNo">105</span>   */<a name="line.105"></a>
<span class="sourceLineNo">106</span>  public static &lt;X extends Throwable&gt; void propagateIfPossible(<a name="line.106"></a>
<span class="sourceLineNo">107</span>      @Nullable Throwable throwable, Class&lt;X&gt; declaredType) throws X {<a name="line.107"></a>
<span class="sourceLineNo">108</span>    propagateIfInstanceOf(throwable, declaredType);<a name="line.108"></a>
<span class="sourceLineNo">109</span>    propagateIfPossible(throwable);<a name="line.109"></a>
<span class="sourceLineNo">110</span>  }<a name="line.110"></a>
<span class="sourceLineNo">111</span><a name="line.111"></a>
<span class="sourceLineNo">112</span>  /**<a name="line.112"></a>
<span class="sourceLineNo">113</span>   * Propagates {@code throwable} exactly as-is, if and only if it is an<a name="line.113"></a>
<span class="sourceLineNo">114</span>   * instance of {@link RuntimeException}, {@link Error}, {@code declaredType1},<a name="line.114"></a>
<span class="sourceLineNo">115</span>   * or {@code declaredType2}.  In the unlikely case that you have three or more<a name="line.115"></a>
<span class="sourceLineNo">116</span>   * declared checked exception types, you can handle them all by invoking these<a name="line.116"></a>
<span class="sourceLineNo">117</span>   * methods repeatedly. See usage example in {@link<a name="line.117"></a>
<span class="sourceLineNo">118</span>   * #propagateIfPossible(Throwable, Class)}.<a name="line.118"></a>
<span class="sourceLineNo">119</span>   *<a name="line.119"></a>
<span class="sourceLineNo">120</span>   * @param throwable the Throwable to possibly propagate<a name="line.120"></a>
<span class="sourceLineNo">121</span>   * @param declaredType1 any checked exception type declared by the calling<a name="line.121"></a>
<span class="sourceLineNo">122</span>   *     method<a name="line.122"></a>
<span class="sourceLineNo">123</span>   * @param declaredType2 any other checked exception type declared by the<a name="line.123"></a>
<span class="sourceLineNo">124</span>   *     calling method<a name="line.124"></a>
<span class="sourceLineNo">125</span>   */<a name="line.125"></a>
<span class="sourceLineNo">126</span>  public static &lt;X1 extends Throwable, X2 extends Throwable&gt;<a name="line.126"></a>
<span class="sourceLineNo">127</span>      void propagateIfPossible(@Nullable Throwable throwable,<a name="line.127"></a>
<span class="sourceLineNo">128</span>          Class&lt;X1&gt; declaredType1, Class&lt;X2&gt; declaredType2) throws X1, X2 {<a name="line.128"></a>
<span class="sourceLineNo">129</span>    checkNotNull(declaredType2);<a name="line.129"></a>
<span class="sourceLineNo">130</span>    propagateIfInstanceOf(throwable, declaredType1);<a name="line.130"></a>
<span class="sourceLineNo">131</span>    propagateIfPossible(throwable, declaredType2);<a name="line.131"></a>
<span class="sourceLineNo">132</span>  }<a name="line.132"></a>
<span class="sourceLineNo">133</span><a name="line.133"></a>
<span class="sourceLineNo">134</span>  /**<a name="line.134"></a>
<span class="sourceLineNo">135</span>   * Propagates {@code throwable} as-is if it is an instance of<a name="line.135"></a>
<span class="sourceLineNo">136</span>   * {@link RuntimeException} or {@link Error}, or else as a last resort, wraps<a name="line.136"></a>
<span class="sourceLineNo">137</span>   * it in a {@code RuntimeException} then propagates.<a name="line.137"></a>
<span class="sourceLineNo">138</span>   * &lt;p&gt;<a name="line.138"></a>
<span class="sourceLineNo">139</span>   * This method always throws an exception. The {@code RuntimeException} return<a name="line.139"></a>
<span class="sourceLineNo">140</span>   * type is only for client code to make Java type system happy in case a<a name="line.140"></a>
<span class="sourceLineNo">141</span>   * return value is required by the enclosing method. Example usage:<a name="line.141"></a>
<span class="sourceLineNo">142</span>   * &lt;pre&gt;<a name="line.142"></a>
<span class="sourceLineNo">143</span>   *   T doSomething() {<a name="line.143"></a>
<span class="sourceLineNo">144</span>   *     try {<a name="line.144"></a>
<span class="sourceLineNo">145</span>   *       return someMethodThatCouldThrowAnything();<a name="line.145"></a>
<span class="sourceLineNo">146</span>   *     } catch (IKnowWhatToDoWithThisException e) {<a name="line.146"></a>
<span class="sourceLineNo">147</span>   *       return handle(e);<a name="line.147"></a>
<span class="sourceLineNo">148</span>   *     } catch (Throwable t) {<a name="line.148"></a>
<span class="sourceLineNo">149</span>   *       throw Throwables.propagate(t);<a name="line.149"></a>
<span class="sourceLineNo">150</span>   *     }<a name="line.150"></a>
<span class="sourceLineNo">151</span>   *   }<a name="line.151"></a>
<span class="sourceLineNo">152</span>   * &lt;/pre&gt;<a name="line.152"></a>
<span class="sourceLineNo">153</span>   *<a name="line.153"></a>
<span class="sourceLineNo">154</span>   * @param throwable the Throwable to propagate<a name="line.154"></a>
<span class="sourceLineNo">155</span>   * @return nothing will ever be returned; this return type is only for your<a name="line.155"></a>
<span class="sourceLineNo">156</span>   *     convenience, as illustrated in the example above<a name="line.156"></a>
<span class="sourceLineNo">157</span>   */<a name="line.157"></a>
<span class="sourceLineNo">158</span>  public static RuntimeException propagate(Throwable throwable) {<a name="line.158"></a>
<span class="sourceLineNo">159</span>    propagateIfPossible(checkNotNull(throwable));<a name="line.159"></a>
<span class="sourceLineNo">160</span>    throw new RuntimeException(throwable);<a name="line.160"></a>
<span class="sourceLineNo">161</span>  }<a name="line.161"></a>
<span class="sourceLineNo">162</span><a name="line.162"></a>
<span class="sourceLineNo">163</span>  /**<a name="line.163"></a>
<span class="sourceLineNo">164</span>   * Returns the innermost cause of {@code throwable}. The first throwable in a<a name="line.164"></a>
<span class="sourceLineNo">165</span>   * chain provides context from when the error or exception was initially<a name="line.165"></a>
<span class="sourceLineNo">166</span>   * detected. Example usage:<a name="line.166"></a>
<span class="sourceLineNo">167</span>   * &lt;pre&gt;<a name="line.167"></a>
<span class="sourceLineNo">168</span>   *   assertEquals("Unable to assign a customer id",<a name="line.168"></a>
<span class="sourceLineNo">169</span>   *       Throwables.getRootCause(e).getMessage());<a name="line.169"></a>
<span class="sourceLineNo">170</span>   * &lt;/pre&gt;<a name="line.170"></a>
<span class="sourceLineNo">171</span>   */<a name="line.171"></a>
<span class="sourceLineNo">172</span>  public static Throwable getRootCause(Throwable throwable) {<a name="line.172"></a>
<span class="sourceLineNo">173</span>    Throwable cause;<a name="line.173"></a>
<span class="sourceLineNo">174</span>    while ((cause = throwable.getCause()) != null) {<a name="line.174"></a>
<span class="sourceLineNo">175</span>      throwable = cause;<a name="line.175"></a>
<span class="sourceLineNo">176</span>    }<a name="line.176"></a>
<span class="sourceLineNo">177</span>    return throwable;<a name="line.177"></a>
<span class="sourceLineNo">178</span>  }<a name="line.178"></a>
<span class="sourceLineNo">179</span><a name="line.179"></a>
<span class="sourceLineNo">180</span>  /**<a name="line.180"></a>
<span class="sourceLineNo">181</span>   * Gets a {@code Throwable} cause chain as a list.  The first entry in the<a name="line.181"></a>
<span class="sourceLineNo">182</span>   * list will be {@code throwable} followed by its cause hierarchy.  Note<a name="line.182"></a>
<span class="sourceLineNo">183</span>   * that this is a snapshot of the cause chain and will not reflect<a name="line.183"></a>
<span class="sourceLineNo">184</span>   * any subsequent changes to the cause chain.<a name="line.184"></a>
<span class="sourceLineNo">185</span>   *<a name="line.185"></a>
<span class="sourceLineNo">186</span>   * &lt;p&gt;Here's an example of how it can be used to find specific types<a name="line.186"></a>
<span class="sourceLineNo">187</span>   * of exceptions in the cause chain:<a name="line.187"></a>
<span class="sourceLineNo">188</span>   *<a name="line.188"></a>
<span class="sourceLineNo">189</span>   * &lt;pre&gt;<a name="line.189"></a>
<span class="sourceLineNo">190</span>   * Iterables.filter(Throwables.getCausalChain(e), IOException.class));<a name="line.190"></a>
<span class="sourceLineNo">191</span>   * &lt;/pre&gt;<a name="line.191"></a>
<span class="sourceLineNo">192</span>   *<a name="line.192"></a>
<span class="sourceLineNo">193</span>   * @param throwable the non-null {@code Throwable} to extract causes from<a name="line.193"></a>
<span class="sourceLineNo">194</span>   * @return an unmodifiable list containing the cause chain starting with<a name="line.194"></a>
<span class="sourceLineNo">195</span>   *     {@code throwable}<a name="line.195"></a>
<span class="sourceLineNo">196</span>   */<a name="line.196"></a>
<span class="sourceLineNo">197</span>  @Beta // TODO(kevinb): decide best return type<a name="line.197"></a>
<span class="sourceLineNo">198</span>  public static List&lt;Throwable&gt; getCausalChain(Throwable throwable) {<a name="line.198"></a>
<span class="sourceLineNo">199</span>    checkNotNull(throwable);<a name="line.199"></a>
<span class="sourceLineNo">200</span>    List&lt;Throwable&gt; causes = new ArrayList&lt;Throwable&gt;(4);<a name="line.200"></a>
<span class="sourceLineNo">201</span>    while (throwable != null) {<a name="line.201"></a>
<span class="sourceLineNo">202</span>      causes.add(throwable);<a name="line.202"></a>
<span class="sourceLineNo">203</span>      throwable = throwable.getCause();<a name="line.203"></a>
<span class="sourceLineNo">204</span>    }<a name="line.204"></a>
<span class="sourceLineNo">205</span>    return Collections.unmodifiableList(causes);<a name="line.205"></a>
<span class="sourceLineNo">206</span>  }<a name="line.206"></a>
<span class="sourceLineNo">207</span><a name="line.207"></a>
<span class="sourceLineNo">208</span>  /**<a name="line.208"></a>
<span class="sourceLineNo">209</span>   * Returns a string containing the result of<a name="line.209"></a>
<span class="sourceLineNo">210</span>   * {@link Throwable#toString() toString()}, followed by the full, recursive<a name="line.210"></a>
<span class="sourceLineNo">211</span>   * stack trace of {@code throwable}. Note that you probably should not be<a name="line.211"></a>
<span class="sourceLineNo">212</span>   * parsing the resulting string; if you need programmatic access to the stack<a name="line.212"></a>
<span class="sourceLineNo">213</span>   * frames, you can call {@link Throwable#getStackTrace()}.<a name="line.213"></a>
<span class="sourceLineNo">214</span>   */<a name="line.214"></a>
<span class="sourceLineNo">215</span>  public static String getStackTraceAsString(Throwable throwable) {<a name="line.215"></a>
<span class="sourceLineNo">216</span>    StringWriter stringWriter = new StringWriter();<a name="line.216"></a>
<span class="sourceLineNo">217</span>    throwable.printStackTrace(new PrintWriter(stringWriter));<a name="line.217"></a>
<span class="sourceLineNo">218</span>    return stringWriter.toString();<a name="line.218"></a>
<span class="sourceLineNo">219</span>  }<a name="line.219"></a>
<span class="sourceLineNo">220</span>}<a name="line.220"></a>




























































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